Research On Damage Imaging Detection Technology Of Ring Transient Electromagnetic Array Casing

Transient electromagnetic(TEM)method has been widely used in the field of oil & gas resource exploration due to its wide frequency spectrum,eddy current diffusion,and easy realization.With the continuous depending of oil & gas development,high-precision downhole TEM detection has become one of the key technologies for casing inspection in oil and gas wells.This paper proposes a toroidal TEM array imaging detection system based on a tunnel magneto-resistive(TMR)sensor,focusing on the research of multi-channel sensor structure design,circuit optimization,and imaging software design.This paper first introduces the basic principles of TEM downhole detection.Aiming at the problem of high-resolution downhole detection in oil and gas wells,the TEM response of an eccentric sensor off-center probe was studied,and the TEM imaging detection system based on the eccentric array was analyzed.In order to improve the azimuth resolution of casing inspection,by taking advantage of the small size and high accuracy of the TMR magnetic field sensors,the Z-axis sensitive TMR array sensors were arranged along the circumference of the transmitting coil to form a ring.Each TMR sensor corresponds to a different detection area and the detection sector can also obtain a higher circumferential azimuth resolution to ensure high sensitivity and high accuracy.On this basis,the structure of the ring array detection system was designed,in which the power supply circuit,excitation circuit,multi-channel scanning acquisition circuit and single-core cable data transmission circuit of the underground ring TEM array were optimized.In addition,the method of data error correction of the TMR array sensors were studied.Furthermore,the imaging software of the TEM array for casing inspection was designed,and the imaging effect was analyzed.Finally,on the basis of the downhole TEM system with TMR array sensors,the circuit debugging,simulation experiments and field experiments were carried out.The module of sensor,power supply,data acquisition and transmission were tested and the experimental results demonstrated that the TMR array proposed in this paper can effectively improve the circumferential resolution of the casing inspection and improve the performance of downhole TEM system.